Wood and coal have been a principle source of fuel for hundreds of years. Within the last 100 years, petroleum has become the overwhelming primary commodity for the generation of energy. Petroleum has had the advantages of low cost and ease of transportation and storage because of its liquid consistency. Further, petroleum is readily amenable to fractionation and conversion into a variety of valuable industrial products such as fuels, building products, chemical intermediates, and the like.
Recent international economic developments have signaled the inevitable decline of petroleum as the world's supreme industrial commodity. The price of raw petroleum has increased several fold. Also, the consumption of petroleum has been increasing exponentially and concomitantly the world petroleum supply has diminished to less than several decades of proven reserves. Governments and industrial concerns on a priority basis are dedicating increased attention to alternatives to petroleum as sources for fuels and chemical intermediates.
It is known that coal and wood can be liquified by controlled heating in the substantial absence of oxygen. The conversion products are a liquid, gas and char. Representative prior art includes U.S. Pat. Nos. 3,379,638; 3,607,718; 3,640,816; 3,642,608; 3,705,092; 3,849,287; 3,870,621; inter alia.
The destructive distillation of wood to produce charcoal, oils and gases is also well known. It has been reported, for example, that as much as two barrels of oil per ton of tree bark can be obtained by a controlled pyrolysis process. The United States Bureau of Mines, in publication Number 8013 entitled "Conversion of Cellulosic Wastes to Oil," reports 90-99 weight percent conversion of sawdust with 40-60 weight percent yields of oil by reaction with synthesis gas at a temperature of 250.degree.-425.degree. C and a pressure of 1500-4000 psig, in the presence of water and an inorganic catalyst.
Because of compelling economic factors, the technology of coal liquefaction and gasification has been expanding at an accelerated pace. Pioneer developments in the field are represented by Lurgi and Fischer-Tropsch technology. More recent advances in coal liquefaction are described in U.S. Pat. Nos. 1,904,586; 1,955,041; 1,996,009; 2,091,354; 2,174,184; 2,714,086; 3,375,188; 3,379,638; 3,607,718; 3,640,816; 3,642,608; 3,705,092; 3,849,287; 3,870,621; inter alia.
The primary product of such coal liquefaction processes is a mixture of liquid and undissolved solids. The liquid is a solution of coal solubilization products dissolved in the liquefaction solvent. Most of the undissolved solids may be readily separated from the liquid by conventional solid-liquid separation processes such as filtration, centrifugation, sedimentation, hydroclones, and the like.
The prior art provides various methods for the separation of coal liquefaction liquids from undissolved solids. Illustrative of the prior art pertinent to such solid-liquid separation methods are U.S. Pat. Nos. 2,060,447; 2,631,982; 2,774,716; 2,871,181; 2,964,460; 2,989,458; 3,010,893; 3,018,241; 3,275,546; 3,519,553; 3,598,118; 3,607,716; 3,607,717; 3,607,718; 3,607,719; 3,635,814; 3,642,608; 3,687,837; 3,791,956; and Def. Publ. No. 700,485. One of the objectives of the prior art processes is maximum recovery of a coal liquefaction product which is substantially free of mineral matter. Other objectives include sulfur and oxygen removal.
Also receiving high priority attention is the management of municipal, industrial and agricultural solid organic wastes, for reasons of environmental protection and natural resource conservation.
Techniques developed for lignite and cellulosics liquefaction are being studied for solid organic waste conversion. Appell et al. have reported the production of heavy oil by treatment of municipal solid waste with carbon monoxide and water at 380.degree. C and 1500 psig pressure (Proc. Of The Nat. Ind. Solid Wastes Management Conference, pages 375-379, March 1970).
U.S. Pat. No. 3,714,038 describes a method of chemically changing solid waste material into useful organic products by pulping a mixture of organic and inorganic wastes in water to form a slurry, removing inorganics from the slurry, dewatering the slurry, and then either pyrolyzing or hydrogenating the dewatered slurry.
U.S. Pat. No. 3,864,096 discloses a process for converting cellulose into a normally liquid oil, which process consists of contacting the cellulose with water, a reducing gas and an ammonia-producing gas at 300-375.degree. C and a pressure of 100-150 atmospheres.
Other processes for converting solid organic wastes into fuels and chemical products are described in U.S. Pat. Nos. 3,085,038; 3,910,775; 3,926,582; 3,933,577; and the references cited therein.
New programs are being initiated for the development of technology for the provision of carbonaceous fuel products which complement and enhance conventional petroleum or coal-derived energy sources. Alternate innovative processes are being sought which do not depend on high pressures or catalysts for efficient and economic conversion of materials such as solid organic wastes.
There remains a pressing need for new technology for the conversion of coal and organic wastes into high value liquid carbonaceous products to complement and to enhance conventional petroleum derived energy applications.
Accordingly, it is a main object of this invention to provide an improved method for converting solid carbonaceous materials into liquid derivatives having application as fuels.
It is another object of this invention to convert coal into a denitrified and desulfurized synthetic crude oil.
It is another object of the present invention to provide a process for liquefaction of solid carbonaceous materials without the use of high hydrogen pressures or conventional hydrogenation catalysts.
It is another object of the present invention to solubilize cellulosic waste materials such as cardboard and newsprint, grain husks, nut shells, and the like, to form flowable heavy oil or pitch-like compositions which are directly applicable as liquid fuels.
It is a further object of the present invention to upgrade low value refractory petroleum residua from refinery operations into liquid fuel media.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.